The (CFS) scheduler has some extra logic catering to systems with SMT, butthat logic won't be compiled in unless the above config is set.

Note that the SMT-centric codepaths are gated by the sched_smt_presentstatic key, and the SMT sched_domains will only survive if the platform hasSMT. As such, the only impact on !SMT platforms should be a slightlybigger kernel - no behavioural change.

Distro kernels already enable it, which makes sense since there already arethings like ThunderX2 out in the wild. Enable it for the defconfig.